For example, there is a circuit board including a ceramic board having first and second surfaces facing each other, a wiring conductor that is formed on a first surface of the ceramic board and includes a connecting area, which is made of tungsten or molybdenum as a major component and to which a lead terminal is joined via silver solder, and a copper or copper alloy layer formed on a second surface of the ceramic board, as in Japanese Laid-open Patent Application No. 2009-147210.